Indicate import errors dealing with basetypes

Really, all of the initialization functions need to be rewritten like this,
but this was needed to track down a specific import error.
Reduce the logging and printing we do in the Matroska writer
process: FIX: Bad string format code in CodedImageSource
cprocess: FIX: Reset subsample framebuffer for next pass

We reuse the framebuffer now, so I can't just leave glDrawBuffers pointing
to two color buffers, or I get corrupted textures.
Add the video encoder script I'm using for my private project

This uses the libdv audio decoder right now because I'm testing it. The
libdv decoder is still producing a big time offset after errors, and worse,
it goes silent after fifteen or twenty minutes, so I'm going to have to
diagnose that. The first problem may just be down to re-syncing to the
video PTS on errors.